\subsection{Quality Testing}
Usage analysis can be used to test of usage of the website for example if links are unreachable or they are being follow they way they were intended. It can also be used to find erratic behavior on the website like a link that directs to the wrong path.

To able to take usage analysis into account it would be necessary to extend the typical web log and then analyze it using a library such as log4php.

If we where to test a new functionality for the website www.coolshop.dk using A/B testing we would expose half the user base to the website with the new functionality and the other half to the website without the new functionality. When the users have used the website their log files are processed, afterwards the results are analyzed and compared to each other to see if the new functionality had the desired effect, such as increase the amount of orders or the like.
To implement usage analysis extensions we would use the log4php library. In the super class we would include the library which we would configure through an xml file. When this is done we can start constructing our log messages and set their types, such as "trace", "debug" and "warn". The messages can be configured to only be shown if they are of a certain type so when the users navigates through the website each message will be logged when appropriate.

The advantages of the A/B testing is that it can provide a concrete measure on how big an impact the new functionality will have whether positive or negative. 

The disadvantages of the A/B testing is that there are additional overhead on the logging and analysis of the test data. If a user finds the website during the testing of the new functionality and then recommends it to friend who then does not get the to try the new functionality it could cause confusion and/or frustration.